1. Field of the Invention
The present invention relates to a method of manufacturing an ink jet print head that ejects a print liquid such as ink through ejection ports for printing.
2. Description of the Related Art
An ink jet printing apparatus is based on what is called a non-impact printing scheme and characterized by making almost no noise during printing and being capable of printing various print media at a high speed. Thus, the ink jet printing apparatus is widely adopted to serve as a printing mechanism for a printer, a copier, a facsimile machine, and a word processor.
Typical ink ejecting schemes for a print head mounted in the ink jet printing apparatus use electromechanical transducers or irradiate ink with an electromagnetic wave such as laser so that the ink generates heat to allow ink droplets to be thermally ejected. Another known scheme uses electrothermal transducing elements that are heating resistors to heat the ink to cause film boiling, allowing the ink droplets to be ejected.
According to the scheme for the ink jet print head using the electrothermal transducing elements, the electrothermal transducing elements are provided in a print liquid chamber, and electric pulses that are print signals are applied to the elements, which thus generate heat to apply thermal energy to the ink. The scheme utilizes the pressure of air bubbles generated by a change in the phase of the ink when the electrothermal transducing elements generate heat, to eject the ink through fine ejection ports to print a print medium. The ink jet print head using the electrothermal transducing elements generally has ejection ports through which the ink droplets are ejected and ink channels through which the ink is fed to the ejection ports.
The ink jet print head includes a tank replaceable type in which ink tanks storing the ink and a print head section are removable and a type in which the print head section and the ink tanks are integrated together. In the type in which the print head section and the ink containers are integrated together, when the ink is exhausted, the ink jet print head as a whole is replaced with a new one. Thus, a user can always be provided with a new print head.
With reference to FIGS. 15A, 15B, and 16, a conventional common color ink jet print head 701 will be described which ejects yellow ink, magenta ink, and cyan ink for printing.
FIG. 15A is a perspective view of the conventional common color ink jet print head 701 clearly showing a bottom surface portion thereof. FIG. 15B is a perspective view of the conventional common color ink jet print head 701 clearly showing a top surface portion thereof. The ink jet print head 701 includes an ink jet print head section including a printing element substrate 1001, and an ink tank section containing ink; the ink jet print head section and the ink tank section are integrated together. The printing element substrate 1001 is composed of a substrate comprising wiring through which electric energy to be supplied to electrothermal transducing elements is transmitted, an ink supply port through which the ink is fed to the area in which the electrothermal transducing elements are arranged, and ink ejection ports through which the ink is ejected. The single printing element substrate 1001 comprises the ejection ports through which the three color inks, the yellow ink, the magenta ink, and the cyan ink, are ejected.
FIG. 16 is an exploded perspective view of a conventional ink jet print head. An electric wiring substrate 301 transmits electric signals to a printing element substrate 101, and inputs electric signals from the ink jet printing apparatus to the printing element substrate 101 via external signal input terminals 303. The electric wiring substrate 301 and the printing element substrate 101 are connected together by electrode terminals (not shown in the drawings) arranged on the printing element substrate 101 and flying leads 302 arranged on the electric wiring substrate 301. The connection section between the electric wiring substrate 301 and the printing element substrate 101 is covered with an electrode sealing compound 203 shown in FIG. 15A and thus protected from the ink.
The ink fed to the printing element substrate 101 is housed in an ink storage section (not shown in the drawings) enclosed by a support member 501 and a cover 503 (see FIG. 15B) to hold and store the color ink. An ink absorbent (not shown in the drawings) that holds the ink is housed in the ink storage section. A filter (not shown in the drawings) is provided in an ink supply channel 502 through which the ink is fed to a print head section provided inside the support member 501. The filter prevents foreign matter from entering ink ejection ports formed in the printing element substrate 101.
Common materials for the support member 501 include alumina and resin. However, in spite of the disadvantage of reducing the accuracy of a printing element substrate bonding surface of the support member 501, the resin advantageously allows the support member 501 to be manufactured more inexpensively than the alumina. A common adhesive used to bond the printing element substrate 101 and the electric wiring substrate 301 is of a thermosetting type that is easy to handle during a manufacturing process or of a hardening type using both light and heat.
In connection with a common process of manufacturing an ink jet print head 701, a method will be described below which bonds the printing element substrate 101 and the electric wiring substrate 301 to the support member 501.
First, in a bonding surface treatment step, a surface of the support member 501, to which the printing element substrate 101 and the electric wiring substrate 301 are bonded, is treated. Common surface treatments include plasma treatment and washing. Such a surface treatment allows improvement of the bonding strength exhibited when the substrate or the like is bonded to the support member subjected to the surface treatment.
Now, temporary hardening of an adhesive 201 will be described. In a step of bonding the printing element substrate 101, the adhesive 201 is coated on a recess portion 504 of the support member 501 to which the printing element substrate 101 is bonded. A printing element unit 401 made up of the printing element substrate 101 and the electric wiring substrate 301 is then applied to the recess portion 503. At this time, the position to which the printing element unit 401 is applied is adjusted by image processing or the like so that the printing element substrate 401 is applied at a predetermined accuracy. In the supplied printing element unit 401, the printing element substrate 101 and the electric wiring substrate 301 are already joined together. The adhesive 201 between the support member 501 and the printing element unit 401 has not been hardened yet. Thus, the printing element unit 401 moves and deviates from the predetermined application accuracy. Thus, in the apparatus to which the printing element unit 401 is applied, the adhesive 201 needs to be temporarily hardened so as to prevent the printing element unit 401 from being moved by vibration or the like during a transfer to the next step. Then, in the common manufacturing method, the adhesive 201 is fully hardened during a step following the temporary hardening.
Japanese Patent Laid-Open No. 2002-154209 discloses a method of hardening an adhesive sticking out from the outer periphery of the printing element substrate sucked and held by a vacuum finger by irradiating the adhesive with ultraviolet rays.
FIG. 17 shows a method of hardening an adhesive, described in Japanese Patent Laid-Open No. 2002-154209.
Furthermore, a method utilizing ultraviolet rays as a heat source irradiates the surface of the printing element substrate with ultraviolet rays 902 via an ultraviolet irradiation lens 901 to heat the printing element substrate to temporarily harden, via the printing element substrate, the adhesive that is in contact with the printing element.
Japanese Patent Laid-Open No. 2005-305960 discloses a method of forming an opening in the bonding surface of the printing element substrate and directly heating a back surface of the printing element substrate using an external heat source.
Such a method is used to accurately temporarily fix the printing element unit 401 to the support member via the adhesive. Then, in a full adhesive hardening step, the temporarily hardened adhesive 201, which bonds the printing element unit 401 to the support member, is fully hardened using a thermosetting furnace.
The adhesive is hardened using any of the above-described methods. Then, if the temporary hardening is performed by irradiating the adhesive sticking out from the outer periphery of the printing element substrate with ultraviolet rays, completing the temporary hardening of the adhesive requires about five seconds. If the temporary hardening is performed by irradiating the surface of the printing element substrate with the ultraviolet rays as a heat source, completing the temporary hardening of the adhesive requires about ten seconds.
According to the method disclosed in Japanese Patent Laid-Open No. 2002-154209, in connection with the configuration of the apparatus, the vacuum finger adhesively fixing the printing element substrate to the support member sucks and holds the printing element substrate to bond the printing element substrate to the adhesive coated on the support member. However, in this case, since the vacuum finger sucks and holds the printing element substrate, the vacuum finger covers most of the surface of the printing element substrate. Moreover, since a surface of the support member to which the printing element substrate is bonded is recessed, an ultraviolet irradiation area is narrowed by the vacuum finger covering most of the surface of the printing element substrate as well as the recess shape of the support member. This makes it difficult to irradiate the adhesive sticking out from the outer periphery of the printing element substrate with ultraviolet rays.
Thus, since the area that can be irradiated with ultraviolet rays is narrow, a reduced quantity of ultraviolet rays is applied to the adhesive. Consequently, the ultraviolet irradiation time needs to be increased in order to achieve hardening.
Even with the method utilizing ultraviolet rays as a heat source, since the vacuum finger exerts a suction force required to suck and hold the printing element substrate, the vacuum finger covers most of the surface of the printing element substrate. This reduces the area of the printing element substrate which can be irradiated with the ultraviolet rays. Furthermore, even though the surface of the printing element substrate is irradiated with the ultraviolet rays to heat the printing element substrate, heat escape to the vacuum finger sucking and holding the printing element substrate. This increases the time for which the printing element substrate is heated by ultraviolet irradiation, reducing production efficiency.
Furthermore, with the method of directly heating the back surface of the printing element substrate using the external heat source as described in Japanese Patent Laid-Open No. 2005-305960, the printing element substrate needs to have an area other than the ink supply port against which heaters abut to transmit heat. Thus, miniaturizing the printing element substrate is difficult, and this method is thus not preferable in terms of cost reduction. If the area via which heat is transmitted is reduced, a required quantity of heat is transmitted via the small abutting part, the printing element substrate locally and quickly becomes hot to temporarily harden the adhesive. As a result, the walls of the ink channels may be thermally deformed to mix the adjacent inks together.
Moreover, to temporarily harden the adhesive by raising the temperature of the printing element in a short time, the printing element substrate needs to be heated to a higher temperature than in the prior art. As a result, higher heat is transmitted to the electric wiring substrate 301 via electric wiring. The increased temperature of the electric wiring substrate promotes hardening of the adhesive bonding the electric wiring substrate to the support member. Then, in the subsequent step, even with an attempt to compressively bond the adhesive using a compressive bonding tool, the significantly hardened adhesive cannot be spread. This may affect the bonding plane accuracy of the electric wiring substrate 301. When an attempt is made to bond the electric wiring substrate to the support member with the adhesive prevented from being spread, air enters the interior of the adhesive to generate an air path at a bonding interface. During the subsequent step, a sealing compound used to seal the periphery of the electric wiring substrate enters the air path. Since the amount of sealing compound applied to the periphery is specified, the air path generated prevents the periphery of the printing element substrate and the electric wiring from being covered. Thus, the ink or the like may wet the printing element substrate or the electric wiring to degrade electrical quality.